What does I-140 mean?

I-140 is, simply put, the petition form filed to obtain immigrant status (a green card) through employment. So the following categories of people go through the I-140 process:

Eligibility includes:

A. Someone seeking to obtain a green card (immigrant status) through an employer sponsor
B. Someone qualifying under EB-1A or EB-2 NIW as a highly qualified individual, filing independently for a green card without a sponsor

Those falling under either of these two categories go through the I-140 process.